Railway signal system



May 31, 1927.`

1,639,727 'J. L. WOODBRIDGE RAILWAY SIEGNAL SYSTEM Filed Nov. 5a 1921 Patented May 31, 1927.

1,630,727 PATEN'r \oFi=icii.

JOSEPI-I'L. WQODBRIDGE, OF PHILADELPHIA, iPENNSYIiVANIA, y f

. RAILWAY siGNAL sYs'rnM.

Application `flcd vITovembei My invention relates to signa-l systeins employing a track circuit consistingin part ot the two opposite rails o3t` a railway track, these rails constituting a section of the track insiilated at each end troni the adjoiningl `sections. A track circuit oi this kind, which used for conducting currentlo'r actuating relays orsiniilar signal devices, is frequently subject to the interference of so-ca-lled for- `eign or stray currents, originating, tor exainple, in the returncircuit of a neighboring electric railway, Where the trackis used for the return conductor.

One object of iny invention is to furnish simple, reliabie and inexpensive means tor preventing such foreign currents troni4 interfering with the operation ot' the signa-ls and especially 'tor preventing such `foreign currents from giving a talee Clear ii'idication. @ther objects ot the invention will appear troni the olloiving description, in which reference is ina-de to the accompany# ing drawings forming part hereof and in Which' j y vFigure l shows diagraininatically a portion ot a railway signal system embodying features ot my invention and employing `a single auxiliary relay, and l Fig. 2 shows a niodiication ofthe system shown in Figure 1 in which two auxiliary relays are employed.

iii-the drawings 1 and 2 are the opposite rails of a sect-ionot railroad track insulated treinl the adjoining sections at 32,33, Bel and rlhe source of current- 3 here shoivn as a battery is connected across the opposite rails at one end ot the section With a y limiting resistance it in series therewith. A

' 9, l0 supplies current ilor operating signals relay 5 `is located at the opposite end of the track section and is provided. with an exciting coil 6 connected across theopposite rails, so that current troni the source 3 passing over the rails l, 2 and through the coily 6 will hold the relay in the closed position, thereby making electrical connectionv between the contact'- points 7 and 8, and` maintaining the continuity of the signal circuit 9, l() at the relay The signal circuit or signal relays, or similar devices well known in the art, but iuasrnuch as these devices torin no part oli the present invention, they are not here shown. The circuits and apparatus thus taiilescribed farewell known and in coininon use at the present time andare designed to operate as follows:

s, 192i. serial Ng. 512,525.

Then a train is located on the block between the insulating. pointsy 32, at one end, and Set, 35 at the' other, the Wheels and axles constituteV la loiv resistance shunt across the rails l, 2, which reduces the voltage between the rails l, 2 and diverts current from the coil 6 to such an extent that the relay 5 is permitted to open and vthe circuit is broken between the contacts T and 8, and the current is interrupted in the signal circuit 9, 10. This interruption ot current operates the signalsto give a Stop 01"Caution7 indication, as the case inay be. Similarly, it

there is a broken rail on either side of the r track between the points of connection ot'tlie source il and the points Where the coil (i is connected, the current in the coil 5 Will be interrupted and the signals Willloe set to give a Stopj or Caution indication. It sometimes occurs, however, that in the case of a brokenrail or oli a train on theblock ivitli a high resistance joint inthe track between the train and the coil 6, that stray currents from the ground, with Which the rails may be in contact, Will pass through the coil 6', vand hold the relay closed, thus causing the signals to give a false Cleai indication. In order to prevent this result,

`I have shown in Figure l, an auxiliary n circuit across the contacts 14, l5 will be` opened, and the ettect will be thc saine as it the contacts of the relay 5 were opened; that is, a CStop ory Caution indication will be given by the signals controlled by the circuit 9, l0. Coil 12 connected acrossmthe opposite ends of rail l by means ot conductor 18, While coil lf3 is connected 'acrossthe opposite ends of rail 2 by means ot conductor 19. y v` y e -Under iiorinal conditions, assuming the Vpositive terminal ot the 'source 3 tolie con nec-ted to rail l, tlicjfcurrent- 'frointlie source 3 Will loiv along rail l and through coil and back tlnfoughrail `2. This current will produce a sinall voltageidrop in rail lV and electric current connected across said rails at one point and a relay with its actuating 15 coil connected across said rails at another point and its contacts connected -lnto` the signal operating circuit, and'auxlhary means adapted to open said signal operating cir-` cuit, said means provided with two actuating` coils, whereof one is connected between separated points of one of said rails and the other is connected across separated points of the other rail.

K JOSEPH L. WOODBRIDGE. 

